Structure and Optical, Electrical, and Adhesive Characteristics of CoFeB Thin Films

This study investigated the structure and thermal, electrical, optical, and adhesive properties of two magnetic CoFeB thin films with compositions of Co40Fe40B20 and Co60Fe20B20. The thin films were deposited on a glass substrate by using direct current (DC) magnetron sputtering at room temperature (RT) and ranged in thicknesses from 25 to 200 angstrom. X-ray diffraction (XRD) patterns indicated that the thin films were amorphous. The activation energy (Q) of the Co40Fe40B20 and Co60Fe20B20 thin films exhibited concave up and concave down trends, respectively. The critical thickness of the films was 75 angstrom. The 75-angstrom-thick Co60Fe20B20 thin film exhibited the highest Q value, indicating that transforming the amorphous structure into a crystalline structure is difficult. When the Co concentration ratio was increased, the stability of the amorphous state of CoFeB increased apparently. The 75-angstrom-thick Co60Fe20B20 thin film exhibited the highest resistivity, whereas the 75-angstrom-thick Co40Fe40B20 thin film exhibited the lowest resistivity. As the thickness of the Co40Fe40B20 and Co60Fe20B20 thin films was increased, the transmittance decreased and absorbance increased. The Co60Fe20B20 thin film exhibited a higher surface energy and stronger adhesion than did the Co40Fe40B20 thin film.